Honeycomb structure and assembly thereof

ABSTRACT

A honeycomb structure obtained by bonding, into one piece, a plurality of honeycomb segments ( 2 ) each having a plurality of passages ( 6 ) surrounded by cell walls and extending in the axial direction of the segment. In the honeycomb structure, a material A ( 3 ) having compressive elasticity is provided between a side surface ( 21 ) of at least one honeycomb segment [2( a )] not constituting the outermost peripheral surface ( 23 ) of the honeycomb structure ( 1 ) and a side surface of the honeycomb segment [(2( b )) adjacent thereto. A honeycomb structure assembly ( 8 ) obtained by providing a material B ( 5 ) having compressive elasticity on the outermost peripheral surface ( 23 ) of the honeycomb structure ( 1 ) in a compressed state and thereby compression-holding the resulting honeycomb structure in a metallic container ( 11 ). A honeycomb structure using materials having compressive elasticity (B) is resistant to breakage, and has superior durability and reliability, by reducing the thermal stress generated therein during use by a sharp temperature change of inflow gas, a local heat of reaction and a local heat of combustion.

BACKGROUND

1. Technical Field

The present invention relates to a honeycomb structure used in, forexample, a catalyst carrier utilizing a catalytic action, for use in aninternal combustion engine, a boiler, a chemical reactor, a fuel cellreformer, etc., a filter for trapping fine particles present in anexhaust gas, and to an assembly thereof. More particularly, the presentinvention relates to a honeycomb structure that is resistant to breakswhen exposed to a thermal stress during its use, as well as to anassembly thereof.

2. Background Art

Honeycomb structures are in use in, for example, a carrier for acatalyst having a catalytic action, for use in an internal combustionengine, a boiler, a chemical reactor, a fuel cell reformer, etc., and afilter for trapping fine particles present in an exhaust gas,particularly fine particles emitted from a diesel engine.

In a honeycomb structure used for such a purpose, a sharp temperaturechange of exhaust gas and local heating make non-uniform the temperaturedistribution inside the honeycomb structure, and there have beenproblems such as crack generation in the honeycomb structure and thelike. When the honeycomb structure is used particularly as a filter fortrapping a particulate matter in an exhaust gas emitted from a dieselengine, it is necessary to burn the fine carbon particles deposited onthe filter to remove the particles and regenerate the filter and, inthat case, high temperatures are inevitably generated locally in thefilter; as a result, large thermal stress and cracks tend to begenerated.

Hence, there have been proposed processes for producing a honeycombstructure by bonding a plurality of individual segments using anadhesive. For example, U.S. Pat. No. 4,335,783 discloses a process forproducing a honeycomb structure that comprises bonding a large number ofhoneycomb parts using a discontinuous adhesive. Also, JP-B-61-51240proposes a thermal-shock resistant rotary regenerative heat exchangerthat is formed by extrusion molding a matrix segment of honeycombstructure made of a ceramic material; cutting the structure intosegments; firing them; making smooth, by processing, the outerperipheral portion of a fired segment; coating the part subject tobonding of the resulting segment with a ceramic adhesive which turns,after firing, to have substantially the same chemical composition as thematrix segment and a difference in thermal expansion coefficient of 0.1%or less at 800° C.; and firing the coated segments. Also, SAE paper860008 (1986) discloses a ceramic honeycomb structure obtained bybonding cordierite honeycomb segments with a cordierite cement. Further,JP-A-8-28246 discloses a ceramic honeycomb structure obtained by bondinghoneycomb ceramic members with an elastic sealant made of at least athree-dimensionally intertwined inorganic fiber, an inorganic binder, anorganic binder and inorganic particles.

Meanwhile, regulations for exhaust gas have become stricter and engineshave come to have higher performances. As a result, in order to achievean improvement in combustion conditions of an engine and an increase inpurification ability of a catalyst, the temperature of exhaust gas hasincreased year by year. In this connection, a higher thermal shockresistance has come to be required for the honeycomb substrate.Therefore, even with honeycomb structures such as mentioned above, whena sharp temperature change of inflow gas takes place, and a local heatof reaction, a local heat of combustion, etc., becomes larger duringuse, it is possible that the thermal stress applied thereto may not besufficiently relaxed, cracks may appear therein and, in an extreme case,for example, the honeycomb structure may begin to disintegrate and breakinto fine pieces due to vibration.

The present invention has been made in view of the above situation. Itaims at providing a honeycomb structure which resists breakage, andaccordingly has superior durability and reliability, by reducing thethermal stress generated therein during use by a sharp temperaturechange of inflow gas, a local heat of reaction and a local heat ofcombustion.

SUMMARY OF THE INVENTION

In a first aspect, the present invention provides a honeycomb structureobtained by bonding, into one piece, a plurality of honeycomb segmentshaving a large number of passages surrounded by cell walls and extendingin the axial direction of the segment, characterized in that a materialA having compressive elasticity is provided between a side surface of atleast one honeycomb segment that is not constituting the outermostperipheral surface of the honeycomb structure and a side surface of thehoneycomb segment adjacent to the at least one honeycomb segment.

In this aspect, it is preferred that a material having compressiveelasticity is provided at part or the whole of the space between twoadjacent honeycomb segments constituting the outermost peripheralsurface of the honeycomb structure. It is also preferred that thematerial A having compressive elasticity is a ceramic fiber-made mat,and it is further preferred that the ceramic fiber-made mat is anon-intumescent mat composed mainly of alumina or mullite. It is alsopreferable that the honeycomb structure of the first invention is usedfor purification of exhaust gas of an automobile, and it is furtherpreferable that the honeycomb structure is used as a filter for trappingdiesel particulate. In this aspect, it is also preferable that the maincomponent of the honeycomb segment comprises (1) at least one kind ofceramic selected from the group consisting of silicon carbide, siliconnitride, cordierite, alumina, mullite, zirconia, zirconium phosphate,aluminum titanate, titania, and combinations thereof; and (2) Fe—Cr—Al,nickel, or a material comprising metallic Si and SiC.

In a second aspect, the present invention provides a honeycomb structureassembly obtained by providing a material B having compressiveelasticity, on the outer peripheral portion of the above honeycombstructure in a compressed state, thereby compression-holding thehoneycomb structure in a metallic container.

In the second aspect, the material B having compressive elasticity ispreferably a ceramic fiber-made mat, further preferably aheat-intumescent mat containing vermiculite, more preferably anon-intumescent mat composed mainly of alumina or mullite. The honeycombstructure assembly is preferably a canned structure obtained by astuffing method, a tourniquet method, a clamshell method or a swagingmethod. Further, the honeycomb structure assembly is preferably obtainedby loading a catalyst on honeycomb segments and then accommodating thecatalyst-loaded honeycomb segments in a metallic container.Alternatively, the honeycomb structure assembly is preferably obtainedby accommodating honeycomb segments in a metallic container and thenloading a catalyst on the honeycomb segments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1( a) is a schematic top view showing one embodiment of thehoneycomb structure of the present invention. FIGS. 1( b) and 1(c) areeach a schematic top view of a honeycomb segment(s).

FIG. 2 is a schematic top view showing one embodiment of the honeycombstructure assembly of the present invention.

FIG. 3 is a partially cut-away view showing one example of the stuffingmethod used for stuffing a honeycomb structure in a metallic container.

FIG. 4 is a perspective view showing one example of the tourniquetmethod used for accommodating a honeycomb structure in a metalliccontainer.

FIG. 5 is a perspective view showing one example of the clamshell methodused for accommodating a honeycomb structure in a metallic container.

FIG. 6 is a sectional view parallel to the direction of passage, showingone example of the swaging method used for accommodating a honeycombstructure in a metallic container.

FIG. 7 is a sectional view parallel to the direction of passage, showingone example of the swaging method used for accommodating a honeycombstructure in a metallic container.

FIG. 8 is a schematic top view of the honeycomb structure produced inExample 1.

FIG. 9( a) is a schematic top view of the honeycomb structure producedin Example 2, and FIG. 9( b) is a schematic top view of a bondedhoneycomb segment.

FIG. 10( a) is a schematic top view of the honeycomb structure producedin Example 3, and FIG. 10( b) is a schematic top view of a bondedhoneycomb segment.

FIG. 11( a) is a schematic top view of the honeycomb structure producedin Example 4, and FIG. 11( b) and 11(c) are each a schematic top view ofrespective bonded honeycomb segments.

FIG. 12( a) is a schematic top view of the honeycomb structure producedin Example 5, and FIG. 12( b) is a schematic top view of a bondedhoneycomb segment.

FIGS. 13( a) and 13(b) are each a schematic top view of the honeycombstructure produced in Comparative Example. FIG. 13( a) shows thehoneycomb structure of Comparative Example 1; and 13(b) shows thehoneycomb structure of Comparative Example 2.

FIG. 14 is a graph showing the result of a test for evaluation ofbreakage limit.

DETAILED DESCRIPTION OF EMBODIMENTS

The honeycomb structure and the honeycomb structure assembly of thepresent invention are described in detail below with reference to theaccompanying drawings. However, the present invention is not restrictedto the following embodiment. Incidentally, in the following, “section”refers to a section vertical to the direction of passage unlessotherwise specified.

FIG. 1( a) is a schematic top view showing one embodiment of thehoneycomb structure of the present invention. The honeycomb structure 1of the present invention shown in FIG. 1( a) is constituted by bonding,into one piece, four honeycomb segments 2(b) and two honeycomb segments2(a), all having a large number of passages 6 surrounded by cell wallsand extending in the axial direction of the honeycomb segment, whereinas a material A having compressive elasticity, a ceramic fiber-made mat3 is provided between the side surfaces of each two adjacent honeycombsegments 2(a) and/or 2(b).

The important characteristic of the present invention is that thehoneycomb structure 1 is constituted so that a material A havingcompressive elasticity is provided between the side surface 21 of thehoneycomb segment 2(a) that is not constituting the outermost peripheralsurface 23 of the honeycomb structure 1 and the side surface of thehoneycomb segment 2(b) adjacent thereto. Having such a constitution, thehoneycomb structure of the present invention absorbs displacements ofhoneycomb segments 2(a) and 2(b), which occur during the use of thehoneycomb structure due to a sharp temperature change of inflow gas, alocal heat of reaction, a local heat of combustion, etc.; as a result,the thermal stress generated in the honeycomb structure 1 decreases,breakage of the honeycomb structure 1 is preventable, and also the useof honeycomb structure at higher temperature environment is possible;thus, a honeycomb structure having durability, reliability and also highperformance has been made possible.

In the present invention, “at least one honeycomb segment that is notconstituting the outermost peripheral surface of the honeycombstructure” means, in, for example, FIG. 1( a), one or two honeycombsegments 2(a) that is not constituting the outermost peripheral surface23 of the honeycomb structure 1. When the honeycomb segment notconstituting the outermost peripheral surface 23 is only one honeycombsegment 2(a), its side surface is a side 21 of a half-cylinder shown inFIG. 1( b); when the honeycomb segment not constituting the outermostperipheral surface 23 is two honeycomb segments 2(a), their side surfaceis a side 21 of a cylinder shown in FIG. 1( c). Therefore, in the caseshown in FIG. 1( b), when a ceramic fiber-made mat 3 is provided on theside 21 of a half-cylinder, the same ceramic fiber-made mat 3 may beprovided or an adhesive may be used for bonding without using theceramic fiber-made mat 3 between other side surfaces. In the case shownin FIG. 1( c), when a ceramic fiber-made mat 3 is provided on the side21 of a cylinder, the same ceramic fiber-made mat 3 may be provided oran adhesive may be used for bonding without providing the ceramicfiber-made mat 3 between other side surfaces. Preferably, as shown inFIG. 1( a), the same ceramic fiber-made mat 3 is provided also at thespaces between the side surfaces 25 of two adjacent honeycomb segments2(b) constituting the outermost peripheral surface of the honeycombstructure 1.

In the present invention, the material A having compressive elasticityis preferred to have heat resistance and cushioning. As the compressiveelasticity material A having heat resistance and cushioning, there is anon-intumescent material containing substantially no vermiculite or alow-intumescent material containing a small amount of vermiculite. Sucha material is preferred to contain, as a main component, a ceramic fibermade of at least one kind selected from the group consisting of alumina,high alumina, silicon carbide, silicon nitride, zirconia and titania, orof a composite thereof. Further, the material A having compressiveelasticity is preferred to be a mat made of such a fiber, and theceramic fiber-made mat is preferred to be a non-intumescent mat composedmainly of alumina or mullite. Further preferably, these ceramic-mademats have a sealing property for preventing the leakage of to-be-treatedfluid. Preferred specific examples of the material A having compressiveelasticity are 1100HT™ produced by 3M Co. and Maftec™ produced byMitsubishi Chemical Corporation.

In the present invention, each honeycomb segment 2 is preferred tocontain, as a main component, (1) at least one kind of ceramic selectedfrom the group consisting of silicon carbide, silicon nitride,cordierite, alumina, mullite, zirconia, zirconium phosphate, aluminumtitanate, titania and combinations thereof; and (2) Fe—Cr—Al, nickel; ormetallic Si and SiC, from the standpoints of the strength, heatresistance, etc. In the present invention, “main component” means asubstance which is 80% by mass or more of all components and whichbecomes a main crystalline phase.

The cell density (the number of passages per unit sectional area) of thehoneycomb segment 2 is preferably 0.9 to 310 cells/cm² (6 to 2,000cells/in.²). When the cell density is less than 0.9 cell/cm², thegeometrical surface area is insufficient. When the cell density is morethan 310 cells/cm², the pressure loss is too large. The sectional shape(cell shape) of the passage of the honeycomb segment 2 is preferably anyof a triangle, a tetragon and a hexagon from the standpoint ofproduction.

The section of the honeycomb segment 2 has at least one side ofpreferably 30 mm or more, more preferably 50 mm or more, most preferably70 mm or more from the standpoint of providing the material A havingcompressive elasticity in standpoint of production.

FIG. 2 is a schematic top view of a honeycomb structure assembly 8obtained by holding a honeycomb structure shown in FIG. 1, in a metalliccontainer 11. The honeycomb structure assembly 8 of the presentinvention, shown in FIG. 2, is obtained by providing a material B havingcompressive elasticity, on the outer peripheral portion of a honeycombstructure 1 in a compressed state and thereby compression-holding thehoneycomb structure 1 in a metallic container 11.

In the present invention, the material B having compressive elasticityis preferred to have heat resistance and cushioning, similarly to theabove-mentioned material A having compressive elasticity, and is furtherpreferred to have a sealing property. The material B having compressiveelasticity may be a non-intumescent material or an intumescent material.The material B having compressive elasticity is preferred to be, forexample, a ceramic fiber composed mainly of at least one kind selectedfrom the group consisting of alumina, high alumina, mullite, siliconcarbide, silicon nitride, zirconia and titania, or of a compositethereof, and is further preferred to be a mat made of such a fiber.Specifically, there can be used, for example, 1100HT™ produced by 3M Co.and Maftec™ produced by Mitsubishi Chemical Corporation, both mentionedabove. There can also be used, for example, Interlam Mat™ produced by 3MCo. (an intumescent mat).

In the present invention, as the method for accommodating a honeycombstructure 1 and a material B (5) having compressive elasticity in ametallic container 11 in a compressed state, there are suitably used astuffing method shown in FIG. 3, using a guide 17; a tourniquet methodshown in FIG. 4, which comprises winding a metallic plate 11 c around ahoneycomb structure, pulling the plate to impart a pressure to theoutermost surface of the honeycomb structure, and welding and fixing theto-be-jointed areas of the metallic plate 11 c; and a clamshell methodshown in FIG. 5, which comprises interposing a honeycomb structure 1between two metallic container parts 11 a and 11 b while applying a loadto the parts 11 a and 11 b, and welding the to-be-bonded areas (flanges)16 a and 16 b of the parts 11 a and 11 b to obtain a integratedcontainer. There is also suitably used a method (a swaging method)utilizing metal forming technology, shown in FIG. 6, which comprisesapplying a compression force to a metallic container 11 from the outsidevia a tap (of pressure type) 12 to squeeze the outer diameter of themetallic container 11. There can also be used a method shown in FIG. 7,which comprises squeezing, by metal forming process, the outermostsurface of a metallic container 11 using a processing jig 18 with themetallic container 11 being rotated, that is, a method which comprisessqueezing the outer diameter of a metallic container by rotary forgingand thereby imparting a pressure to the outermost surface of a honeycombstructure accommodated in the metallic container.

When the honeycomb structure or honeycomb structure assembly of thepresent invention is used as a carrier for catalyst in an internalcombustion engine, a boiler, a chemical reactor, a fuel cell reformer,or the like, the honeycomb segments used therein are allowed to loadthereon a metal having a catalytic activity. As representative metalshaving a catalytic activity, there are mentioned Pt, Pd, Rh, etc. It ispreferred that at least one kind of these is loaded on the honeycombsegments.

Meanwhile, when the honeycomb structure or honeycomb structure assemblyof the present invention is used as a filter for trapping and removingthe particulate matter contained in an exhaust gas, for example, as adiesel particulate filter (DPF), it is preferred that the cells ofhoneycomb structure are plugged alternately at each end and the cellwalls of honeycomb structure are used as a filter.

When an exhaust gas containing a particulate matter is taken into ahoneycomb structure constituted by honeycomb segments, from its one endface, the exhaust gas enters the inside of the honeycomb structure fromthose holes not plugged at the one end face, passes through porous cellwalls having a filtration ability, and is discharged from the holes notplugged at the other end. The particulate matter is trapped by the cellwalls at the time of its passing through the cell walls.

As the amount of particulate matter trapped and deposited on cell wallsincreases, an increase in pressure loss takes place rapidly, a load toengine increases, fuel consumption and drivability deteriorate; hence,the deposited particulate matter is burnt and removed periodically by aheating means such as heater or the like, to regenerate the ability ofthe filter. In order to promote the combustion during the regeneration,it is possible to load, on the honeycomb structure, the above-mentionedmetal having a catalyst activity.

In the present invention, in order to load a catalyst on a honeycombstructure assembly 8, there can be used a method which comprises holdinga honeycomb structure 1 in a metallic container 11 prior to catalystloading, to form a honeycomb structure assembly 8, and then loading acatalyst on the honeycomb structure 1. According to this method, therisk of chipping-off or breakage of honeycomb structure during catalystloading can be prevented. It is also preferred that when the honeycombstructure or honeycomb structure assembly of the present invention isused as a catalytic converter, a catalyst component is loaded on ahoneycomb segment 2, then a honeycomb structure 1 is formed, and thestructure is accommodated and held in a metallic container 11.

The present invention is described in more detail below by way ofExamples. However, the present invention is not restricted to theseExamples.

Incidentally, each of the following honeycomb structures of Examples andConventional Examples (Comparative Examples) is a filter used fortrapping diesel particulate, which is made of silicon carbide and has acell wall thickness of 0.38 mm and a cell density (the number of passageper unit sectional area) of 31 cells/cm² and wherein the passages areplugged alternately at each end face of the honeycomb structure and thecell walls function as a filter.

EXAMPLE 1

A silicon carbide powder was used as a raw material. Thereto were addedmethyl cellulose, hydroxypropoxyl methyl cellulose, a surfactant andwater to prepare a plastic material. This puddle (mud) was subjected toextrusion molding, and the resulting extrudate was dried using amicrowave and hot air.

Then, the passages of the extrudate were plugged alternately at each endface of the extrudate with a sealant made of the same material as forthe honeycomb structure to be obtained, in such a way that each end faceof extrudate had a checkerboard pattern appearance. Then, the resultingmaterial was heated for debindering in a N₂ atmosphere and then fired inan Ar atmosphere to obtain four honeycomb segments 2(b) having an outerdiameter of 144 mm, an inner diameter of 73 mm and a length of 152 mmand two half-cylindrical honeycomb segments 2(a) having a diameter of 72mm and a length of 152 mm. These six honeycomb segments 2(a) and 2(b)were bonded into one piece by providing a ceramic fiber-madenon-intumescent mat 3 on the side surfaces 21 of the honeycomb segments2(a) and between the side surfaces 25 of each two adjacent honeycombsegments 2(b) and using a double sided tape, to obtain a honeycombstructure 1. The same ceramic fiber-made non-intumescent mat asmentioned above was wound around the outermost peripheral surface 23 ofthe honeycomb structure 1; the resulting material was stuffed in a SUS409-made metallic container using a tapered jig (a guide), tocompression-fix the segments to each other and also the honeycombstructure to the metallic container, to obtain a cylindrical honeycombstructure assembly having a diameter of 144 mm and a length of 152 mm.

EXAMPLE 2

The five honeycomb segments in total produced in the same manner as inExample 1 as shown in FIG. 9( b), i.e. two quadratic prism-shapedhoneycomb segments 2(c) having a size of 30 mm×30 mm×152 mm, onehoneycomb segment 2(d) and two honeycomb segments 2(e), were bondedusing an adhesive 7 which was a mixture of colloidal silica, an aluminafiber and water, followed by drying, to produce four bonded honeycombsegments 9(a). Similarly, four quadratic prism-shaped honeycomb segments2(c) having a size of 30 mm×30 mm×152 mm were bonded using an adhesive 7which was a mixture of colloidal silica, an alumina fiber and water,followed by drying, to produce one bonded honeycomb segment 9(b), whichdoes not constitute the outermost peripheral surface of the honeycombstructure. Then, the four bonded honeycomb segments 9(a) and the onebonded honeycomb segment 9(b) were bonded into one piece by providing aceramic fiber-made non-intumescent mat 3 on the side surface 21 of thebonded honeycomb segment 9(b) and between the surfaces 25 of each twoadjacent bonded honeycomb segments 9(a) and using a double sided tape,to obtain a honeycomb structure 1 shown in FIG. 9( a). The same ceramicfiber-made non-intumescent mat as mentioned above was wound around theoutermost peripheral surface 23 of the honeycomb structure 1; theresulting material was stuffed in a SUS 409-made metallic containerusing a tapered jig, to compression-fix the segments to each other andalso the honeycomb structure to the metallic container, to obtain acylindrical honeycomb structure assembly having a diameter of 144 mm anda length of 152 mm.

EXAMPLE 3

Four bonded honeycomb segments 9(a) were produced in the same manner asin Example 2. Two quadratic prism-shaped bonded honeycomb segments 9(c)having a size of 30 mm×60 mm×152 mm, shown in FIG. 10( b), were producedby bonding two quadratic prism-shaped honeycomb segments 2(c) having asize of 30 mm×30 mm×152 mm using an adhesive 7 which was a mixture ofcolloidal silica, an alumina fiber and water, followed by drying thebonded material. These six bonded honeycomb segments 9(a) and 9(c) werebonded into one piece by providing a ceramic fiber-made non-intumescentmat 3 on the side surfaces 21 of the bonded materials 9(c) and at thespace between the side surfaces 25 of each two adjacent bonded materials9(a) and using a double sided tape, to obtain a honeycomb structure 1show in FIG. 10( a). The same ceramic fiber-made non-intumescent mat asmentioned above was wound around the outermost peripheral surface 23 ofthe honeycomb structure 1; the resulting material was stuffed in a SUS409-made metallic container using a tapered jig, to compression-fix thesegments to each other and also the honeycomb structure to the metalliccontainer, to obtain a cylindrical honeycomb structure assembly having adiameter of 144 mm and a length of 152 mm.

EXAMPLE 4

Two bonded honeycomb segments 9(c) were produced in the same manner asin Example 3. Four bonded honeycomb segments 9(d) shown in FIG. 11( b)were produced by bonding a total of three honeycomb segments, i.e., onehoneycomb segment 2(c), one honeycomb segment 2(d) and one honeycombsegment 2(e) using an adhesive 7 and then drying the bonded material.Two bonded honeycomb segments 9(e) were produced by bonding twohoneycomb segments 2(c) and two honeycomb segments 2(e) using anadhesive 7 and then drying the bonded material. Then, the two bondedmaterials 9(c), the four bonded materials 9(d) and the two bondedmaterials 9(e) were bonded into one piece by providing a ceramicfiber-made non-intumescent mat 3 on the side surfaces 21 of the bondedmaterials 9(c), at the space between the surfaces 25 of each twoadjacent bonded materials 9(d) and at the space between the sidesurfaces 25 of 9(d) and 9(e), and using a double sided tape, to obtain ahoneycomb structure 1 shown in FIG. 11( a). The same ceramic fiber-madenon-intumescent mat as mentioned above was wound around the outermostperipheral surface 23 of the honeycomb structure 1; the resultingmaterial was stuffed in a SUS 409-made metallic container using atapered jig, to compression-fix the segments to each other and also thehoneycomb structure to the metallic container, to obtain a cylindricalhoneycomb structure assembly having a diameter of 144 mm and a length of152 mm.

EXAMPLE 5

Two bonded honeycomb segments 9(c) and two bonded honeycomb segments9(e) were produced in the same manner as in Example 4. Two bondedhoneycomb segments 9(f) shown in FIG. 12( b) were produced by bonding atotal of six honeycomb segments, i.e., two honeycomb segments 2(c), twohoneycomb segments 2(d) and two honeycomb segments 2(e), using anadhesive 7 and then drying the bonded material. Then, the two bondedmaterials 9(c), the two bonded materials 9(e) and the two bondedmaterials 9(f) were bonded into one piece by providing a ceramicfiber-made non-intumescent mat 3 on the side surfaces 21 of the bondedmaterials 9(c) and at the spaces between the side surfaces 25 of 9(e)and 9(f) and using a double sided tape, to obtain a honeycomb structureshown in FIG. 12( a). The same ceramic fiber-made non-intumescent mat asmentioned above was wound around the outermost peripheral surface 23 ofthe honeycomb structure 1; the resulting material was stuffed in a SUS409-made metallic container using a tapered jig, to compression-fix thesegments to each other and also the honeycomb structure to the metalliccontainer, to obtain a cylindrical honeycomb structure assembly having adiameter of 144 mm and a length of 152 mm.

The effects of the above Examples were evaluated in comparison with thefollowing two conventional samples (Comparative Examples).

COMPARATIVE EXAMPLE 1

Four honeycomb segments 2(x) which had a shape of ¼ of a cylinder havinga diameter of 144 mm and a length of 152 mm and which had a fan-likesection, were bonded into one piece using an adhesive 7 which was amixture of colloidal silica, an alumina fiber and water, and then dried,to obtain a honeycomb structure 1 having a diameter of 144 mm and alength of 152 mm, shown in FIG. 13( a). The ceramic fiber-madenon-intumescent mat was wound around the outermost peripheral surface 23of the honeycomb structure; the resulting material was stuffed in a SUS409-made metallic container using a tapered jig, to compression-fix thehoneycomb structure to the metallic container, to obtain a honeycombstructure assembly.

COMPARATIVE EXAMPLE 2

Twenty four honeycomb segments in total, i.e., twelve quadraticprism-shaped honeycomb segments 2(c) having a size of 30 mm×30 mm×152mm, four honeycomb segments 2(d) and eight honeycomb segments 2(e) werebonded into one piece using the above-mentioned adhesive 7 and dried, toobtain a cylindrical honeycomb structure having a diameter of 144 mm anda length of 152 mm, shown in FIG. 13( b). The ceramic fiber-madenon-intumescent mat was wound around the outermost peripheral surface 23of the honeycomb structure; the resulting material was stuffed in a SUS409-made metallic container using a tapered jig, to compression-fix thehoneycomb structure to the metallic container, to obtain a honeycombstructure assembly.

Each of the thus-obtained honeycomb structure assemblies of Examples 1to 5 and Comparative Examples 1 to 2 was allowed to trap 15 g ofparticulate (hereinafter referred to as soot) discharged from a dieselengine. The soot deposited on the filter was burnt using an exhaust gasof 700° C. (inlet temperature), 10% oxygen concentration and 0.7 Nm³/min(flow rate), then the honeycomb structure was observed. When there wasno breakage of the honeycomb structure, the amount of soot trapped wasincreased by 5 g unit to 20 g, 25 g or the like; and the test wasrepeated until there appeared breakage of the honeycomb structure.

The test results are shown in FIG. 14. In Comparative Examples 1 and 2,the breakage limit soot amounts were 25 g and 20 g, respectively, andthe filter inside maximum temperatures at these amounts were 950° C. and840° C., respectively. Meanwhile, in Examples 1 to 5, the breakage limitsoot amounts were 35 to 45 g and the filter inside maximum temperaturesat these amounts were 1,060 to 1,260° C. The honeycomb structures andassemblies thereof, of the present invention, as compared with those ofComparative Examples, showed that they could be used safely up to largesoot amounts and high temperatures.

INDUSTRIAL APPLICABILITY

As described above, in the honeycomb structure and honeycomb structureassembly of the present invention, a material A having compressiveelasticity is provided between the side surface of at least onehoneycomb segment that is not constituting the outermost peripheralsurface of the honeycomb structure and honeycomb segments adjacent tothe at least one honeycomb segment; therefore, breakage of the honeycombstructure can be prevented at larger soot amounts and highertemperatures, and superior durability and reliability could be shown.

1. A honeycomb structure obtained by bonding, into one piece, aplurality of honeycomb segments having a plurality of passagessurrounded by cell walls and extending in the axial direction of thesegment, wherein a material A having compressive elasticity is providedin an unbonded space between a side surface of at least one honeycombsegment that is not constituting the outermost peripheral surface of thehoneycomb structure and a side surface of the honeycomb segment adjacentto the at least one honeycomb segment.
 2. A honeycomb structureaccording to claim 1, wherein a material having compressive elasticityis provided at part or the whole of the space between two adjacenthoneycomb segments constituting the outermost peripheral surface of thehoneycomb structure.
 3. A honeycomb structure according to claim 1,wherein the material A having compressive elasticity is a ceramicfiber-made mat.
 4. A honeycomb structure according to claim 2, whereinthe material A having compressive elasticity is a ceramic fiber-mademat.
 5. A honeycomb structure according to claim 3, wherein the ceramicfiber-made mat is a non-intumescent mat composed mainly of alumina ormullite.
 6. A honeycomb structure according to claim 4, wherein theceramic fiber-made mat is a non-intumescent mat composed mainly ofalumina or mullite.
 7. A honeycomb structure according to claim 1,wherein the honeycomb structure is an exhaust gas purification filter ofan automobile.
 8. A honeycomb structure according to claim 1, whereinthe honeycomb structure is a filter that traps diesel particulate.
 9. Ahoneycomb structure according to claim 1, wherein the main component ofthe honeycomb segment comprises (1) at least one kind of ceramicselected from the group consisting of silicon carbide, silicon nitride,cordierite, alumina, mullite, zirconia, zirconium phosphate, aluminumtitanate, titania or combinations thereof, and (2) Fe—Cr—Al, nickel, ormetallic Si and SiC.
 10. A honeycomb structure assembly comprising: ametallic container, a honeycomb structure, obtained by bonding, into onepiece, a plurality of honeycomb segments each having a plurality ofpassages surrounded by cell walls and extending in the axial directionof the segment, wherein a material A having compressive elasticity isprovided in an unbonded space between a side surface of at least onehoneycomb segment that is not constituting the outermost peripheralsurface of the honeycomb structure and a side surface of the honeycombsegment adjacent to the at least one honeycomb segment, and a material Bhaving compressive elasticity, wherein the material B having compressiveelasticity is provided on the outermost peripheral surface of thehoneycomb structure in a compressed state and thereby the honeycombstructure is compression-held in the metallic container.
 11. A honeycombstructure assembly according to claim 10, wherein the material B havingcompressive elasticity is a ceramic fiber-made mat.
 12. A honeycombstructure assembly according to claim 11, wherein the ceramic fiber-mademat is a non-intumescent mat composed mainly of alumina or mullite. 13.A honeycomb structure assembly according to claim 11, wherein theceramic fiber-made mat is a heat-intumescent mat containing vermiculite.14. A honeycomb structure assembly according to claim 10, wherein thehoneycomb structure assembly is a canned structure including one of astuffed can structure, a tourniquet can structure, a clamshell canstructure or a swaged can structure.
 15. A honeycomb structure assemblyaccording to claim 10, wherein the honeycomb structure assemblycomprises the metallic container accommodating catalyst-loaded honeycombsegments.
 16. A honeycomb structure assembly according to claim 10,wherein the honeycomb structure assembly comprises honeycomb segmentsaccommodated in the metalliccontainer, the interior of the metalliccontainer and the honeycomb segments being loaded with a catalyst.